Cryopreservation is a common strategy for the preservation of various cells, tissues and biomaterials. Unfortunately, in the absence of a cryoprotective agent (CPA) significant cellular damage occurs. While the use of CPAs such as dimethyl sulfoxide (DMSO) and glycerol mitigate this damage, their toxic nature necessitates removal after thawing and this can adversely affect the functionality and integrity of the recovered cells, tissues or material. During the past decade, our laboratory has studied various classes of naturally occurring biological antifreezes (BAs) found in organisms that inhabit sub-zero environments. BAs control the growth of ice and protect organisms against the cellular damage associated with freezing. Our early work has lead to the development of carbon-linked antifreeze glycoprotein (C-AFGP) analogues that exhibit “custom-tailored” antifreeze activity. In particular, these C-AFGPs are potent inhibitors of ice recrystallization and have been shown to effectively cryopreserve human liver cells in the presence of reduced concentrations of DMSO. Extensive structure-function studies with the C-AFGPs have led to the discovery that small carbohydrate-based molecules (molecular masses 300 AMU) are very effective inhibitors of ice recrystallization at concentrations in the millimolar to sub-millimolar range and that these molecules my have unrealized potential as novel cryoprotectants. Freezing of Human red blood cells (RBCs) requires a cell permeating cryoprotectant to ensure adequate post-thaw recoveries. Typically in North America 40% glycerol is utilized and the sample is frozen slowly, while in many European countries smaller quantities of glycerol are utilized in conjunction with very fast freezing rates. After thawing, the glycerol must be removed prior to transfusion in order to avoid intravascular hemolysis. The automated process of removing the 40% glycerol solution from RBC units can take up to 1 h or more. We have examined a number of small molecule ice recrystallization inhibitors (IRIs) for their ability to freeze human RBCs using only 10–15% glycerol and slow freezing rates. Three IRIs, pBrPhGlc, PMPGlc and 4ClA have proven to be very effective cryoprotectants as evidenced by the amount of post-thaw hemolysis. In addition, some of these molecules are able to protect RBCs from cryoinjury associated with transient warming events (TWEs). This presentation will describe the rational design of small molecule IRIs, assessment of their ability to function as novel cryoprotectants for human RBCs and preliminary investigations into their mechanism of action.